Preparation of ammonium ortho-phosphate agricultural suspensions

ABSTRACT

Wet process phosphoric acid containing iron, aluminum or magnesium compounds as impurities is ammoniated to produce an ammonium phosphate having a gelatinous, colloidal component of iron, aluminum or magnesium ammonium phosphate, the ammonium phosphate is heated to dehydrate the gel structure under conditions to prevent the formation of polyphosphates, and the dried material is comminuted to finely divided particles that produce a stable aqueous suspension when dispersed in water. A water soluble magnesium compound may be added to the phosphoric acid, thereby providing magnesium ammonium phosphate in the product.

llnited States Patent Dancy [4 1 Apr. 18, 1972 54] PREPARATION OFAMMONIUM 3,342,579 9/1967 Frazier ..71/34 0RTH() PHOSPHATE AGRICULTURAL3,464,808 9/1969 Kearns ..71/34 SUSPENSIONS FOREIGN PATENTS ORAPPLICATIONS Inventor: William Dancy, Lakeland, 855,104 11/1952 Germany..71/36 t t l M l & Ch l C [73] Ass1gnee ln erna rona mera sv emlca orPrimary xam ne R e r dman poratlon Assistant Examiner-Bennett H.Levenson Filedl 6, 1968 Attorney-James E. Wolber and Peter Andress [21]Appl. No.: 755,395 ABSTRACT Wet process phosphoric acid containing iron,aluminum or [52] US. Cl ...77ll//363,77l1//3:,C7 magnesium p w asimpuritiesis ammqniated w [51] Int.Cl ..C05b7/00,C05b9/00,C05b13/00 F.3f F havmg a l 58 1 Field of Search ..71/34, 64C, 33, 44, 46 a "P'magnesium ammn" um phosphate, the ammomum phosphate 1s heated todehydrate the gel structure under conditions to prevent the [56]References Cited formation of polyphosphates, and the dried material iscom- UNITED STATES PATENTS minuted to finely divided particles thatproduce a stable aqueous suspension when dispersed in water. A watersoluble mag- 3,019,099 1/1962 Walters ..71/34 nesium compound may beadded to the phosphoric acid, 3,155,490 1l/l96 PP X thereby providingmagnesium ammonium phosphate in the 3,249,421 5/1966 Bigot et a1 ..71/43X pmduch 3,285,731 11/1966 Salutsky et a1 ..71/33 3,320,048 5/1967 Legalet a1. ..71/33 X 8Claims,No Drawings PREPARATION OF AMMONIUMORTHO-PHOSPHATE AGRICULTURAL SUSPENSIONS BACKGROUND OF THE INVENTIONFertilizers commonly are applied to fields either as dry solids or asliquid slurries. Since slurry fertilizers offer certain advantages theiruse has grown rapidly in the past several years and continued growthseems likely.

Slurry fertilizers evolved from the practice of applying concentratednitrogen solutions directly to the soil. Ease of application and lowerdistribution costs prompted the agricultural industry to add other majornutrients such as phosphate and potassium and thereby providemulticomponent solutions. Solubility of some ingredients is limited,however, so that application of such nutrients requires relativelydilute solutions.

Thus it is impractical to use solutions for the application of largeamounts per acre of the more insoluble nutrients. As a result, truefertilizer solutions evolved into slurries so that the concentration ofany ingredient need not be limited by its solubility.

The potential for slurry fertilizers is, of course, significantlyaffected by the economics of the components suitable for use inslurries. In this regard wet process phosphoric acid presents apotentially economic source of phosphate and ammonia presents apotentially economic source of nitrogen. Wet process phosphoric acid isan impure product containing dissolved calcium sulfate, fluorides andfluosilicates, and salts, (e.g., phosphates) of aluminum, iron,magnesium and other metals. Unfortunately, ammoniation of wet processphosphoric acid results in the formation of colloidal gelatinousphosphates which clog slurry distribution equipment. During ammoniationof the wet process acid the iron and aluminum components of the acid areprecipitated as colloidal gelatinous phosphates. Magnesium, present inacid made from high-magnesium phosphate rock (e.g., North Carolina andWestern Rock) also forms colloidal magnesium ammonium phosphate. Thedegree and type of gelling frequently is unpredictable.

The art has attempted to cope with the gel-forming propensity of ironand aluminum by ammoniating relatively expensive superphosphoric acidthat contains, for example, 40 percent or more condensed polyphosphatesto form an ammonium polyphosphate solution which may analyze -34-0. Thecondensed polyphosphates sequester iron and aluminum and prevent themfrom forming colloidal precipitates during the ammoniation. Magnesium isnot effectively sequestered by the superphosphoric acid, however, sothat magnesium presents a constant source of trouble.

It has also been suggested in US. Pat. No. 3,022,153 that urea be addedto the wet process phosphoric acid to complex with iron and aluminumphosphates and that the acid thereafter be ammoniated. The solution,however, is apparently not stable over long periods of time or in thepresence of potassium salts which are, of course, required if a completefertilizer slurry is desired.

Others appear to accept the fact that gels will form and attempt toprovide gels which at least minimize the disadvantages presented by thenormal ammoniation of wet process phosphoric acid. These approachesinclude regulation of the concentration of trivalent metals so thatammoniation will form thixotropic gels (U.S. Pat. No. 3,041,160) and theuse of agitation at 140 to 190 F. to form thin gels (U.S. Pat. No.2,799,563).

For much the same reasons applicable to slurry fertilizers, the gellingtendency of the iron, aluminum and magnesium impurities limits theusefulness of ammoniated wet process phosphoric acid as a reliablesource of nitrogen and phosphate in liquid animal feed supplements. Thepresence of colloidal gelatinous phosphates also clogs conventionalliquid animal feed handling systems.

SUMMARY OF THE INVENTION In accordance with this invention thereisprovided a process which comprises ammoniating phosphoric acidcontaining incidental metallic impurities selected from the groupconsisting of iron, aluminum and magnesium and mixtures thereof toprovide an ammonium-containing phosphate having a gelatinous, colloidalcomponent selected from the group consisting of iron, aluminum andmagnesium ammonium phosphates and mixtures thereof, drying saidammonium-containing phosphate under conditions sufficient to dehydratethe gel structure of the gelatinous component, comminuting saidammonium-containing phosphate to finely divided particles substantiallyall of which pass through a 35 mesh (Tyler standard) screen, anddispersing said particles in water to form an aqueous suspension. Thephosphoric acid is typically a wet process phosphoric acid containingnormally incident impurities selected from the group consisting of iron,aluminum and magnesium compounds and mixtures thereof which precipitateas gelatinous solids upon neutralization of the acid with ammonia. In apreferred embodiment, the dried phosphate is comminuted in the presenceof water to provide directly a stable aqueous suspension.

Stable suspensions containing metal ammonium phosphates selected fromthe group consisting of iron, aluminum and magnesium ammonium phosphatesand mixtures thereof in which said metal ammonium phosphates are presentas finely divided dehydrated particles are also contemplated by thisinvention. These metal ammonium phosphates actually serve as viscositybuilders so that it is not necessary to add viscositybuilding clays tomaintain undissolved solids in suspension.

It has been discovered that the troublesome colloidal gelatinous natureof iron, aluminum and magnesium phosphates can be eliminated and amaterial suitable for stable slurries provided if an ammonium phosphatehaving a colloidal gelatinous component is dried and the dried ammoniumphosphate is then finely comminuted. Colloidal gelatinous iron, aluminumand/or magnesium ammonium phosphates are formed during the ammoniationof phosphoric acid containing iron, aluminum or magnesium but the gelstructure is destroyed by drying to dehydrate. The ammonium phosphates,when finely comminuted, are most appropriate for use in stable aqueousslurries. The matrix that results when the dehydrated product is mixedwith water is friable, and the water insoluble metal phosphates arereadily dispersed by wet comminution. It has been determined that oncethe gel structure is destroyed by dehydration, the iron, aluminum andmagnesium ammonium phosphates behave essentially as inert solids in theaqueous suspension and show substantially no tendency to hydrate orreact to reform troublesome gels even though they are present inextremely finely divided form. When, for example, ammonium phosphateproduced from wet process phosphoric acid is treated in accordance withthis invention to provide finely divided ammonium phosphate slurries,the iron and aluminum phosphates act as inert weighting agents thatactually improve the stability of the slurry. Moreover, since the iron,aluminum and magnesium phosphates are broken up into fine inertparticles that readily disperse to provide a stable suspension, ammoniumphosphates produced by ammoniation of defluorinated wet processphosphoric acid can be employed for liquid animal feed supplements. Thefinely dispersed phosphates do not reform gels and do not clogconventional liquid animal feed handling systems. The suspensions ofthis invention are stable, i.e., at most may need only occasionalagitation if some sedimentation tends to occur. The commercial practiceof agitating suspension fertilizers in product storage tanks once ortwice a day with air spargers or mechanical agitators will maintaincomplete homogeneity of the suspensions of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The wet process phosphoric acidwhich now readily may be employed as a phosphate source for ammoniumphosphates is well-known to the art. Phosphate rock often is acidulatedwith sulphuric acid albeit other mineral acids such as hydrochloricacid, nitric acid or the like also may be employed. Followingacidulation insoluble impurities such as, for example, calcium sulphateand the like are removed to provide a phosphoric acid that may containmetallic impurities such as iron, aluminum or magnesium. Wet processacid can range in P concentration of from about 25 percent to about 55percent and is available as a standard article of commerce. The quantityof the iron, aluminum or magnesium-containing impurities in the wetprocess acid will, of course, vary depending upon the source of thephosphate rock from which the wet process acid is manufactured. Arepresentative 54% P 0 phosphoric acid produced from a Florida phosphaterock may contain as much as about 4.5 percent iron and aluminum (Fe Oand A1 0 commonly referred to as I & A, and as much as about 0.75percent magnesium (as MgO). North Carolina rock that is high inmagnesium may provide a 54 percent acid having as much as 2 percentmagnesium. The iron and aluminum are the primary sources of gellingdifficulties. It has been determined that gel formation will becometroublesome when the metal-containing impurities are present in the wetprocess phosphoric acid in amounts producing a weight ratio of the metalcontent expressed as oxides, e.g., l e- 0 and A1 0 to the P 0 content ofthe acid greater than about 0.05. To the extent that other metals whichare present to some degree in wet process acid may be a potential sourceof gelling difficulties, they are also inactivated by the practice ofthis invention.

Ammoniation of wet process phosphoric acid to form ammonium phosphatesis well-known to the art. Monoammonium phosphate may be produced byammoniating phosphoric acid to form a monoammonium phosphate slurrywhich is added to a blunger with undersize product and then dried toprovide dry granules. An appropriate process is described, inter alia,in Industrial & Engineering Chemistry, 41, pp. 1318-24 (1949).Diammonium phosphate may be produced as described, inter alia, in US.Pat. No. 3,153,574. Wet process phosphoric acid is first pre-neutralizedwith ammonia to form an ammonium phosphate slurry. The slurry,additional ammonia, and undersize final product then are introduced intoan inclined rolling bed of discrete particles. The process may becontrolled so that the heat of reaction produces dry diammoniumphosphate particles from the lower end of the rolling bed. If desired,the particles may be dried in a rotary dryer. The process of US. Pat.No. 3,153,574 can also be employed for the production of monoammoniumphosphate. In this event the total ammoniation can be accomplished inthe pre-neutralizer if desired.

In the event that an ammonium phosphate is desired containing a highermagnesium content than that afforded by the magnesium normally presentin phosphoric acid, a magnesium source may be added during the ammonianeutralization of phosphoric acid. For example, in the production ofdiammonium phosphate as outlined in US. Pat. No. 3,153,574, thephosphoric acid is first pre-neutralized to a NzP O mole ratio of about0.8 to 1.2 to form an ammonium phosphate slurry, which is fed to anammoniator-granulator where the remaining ammonia and magnesium sourceare introduced. Most appropriately magnesium contents of up to 16percent (as MgO dry basis) or more can be provided by adding a watersoluble magnesium salt such as magnesium chloride, magnesium sulfate,magnesium carbonate or a magnesium salt in conjunction with a potassiumsalt as contained in minerals such as langbeinite, leonite, kainite,schoenite or the like to the inclined rolling bed of discrete particleswhich is being ammoniated.

Magnesium ammonium phosphate also can be prepared by the reaction ofmagnesium oxide, a magnesium salt or a magnesium mineral with phosphoricacid, subsequent treatment of the slurry thus obtained with ammonia anddrying. An appropriate process is described, inter alia, in US. Pat. No.2,977,213. When magnesium ammonium phosphate is prepared by theammoniation of wet process phosphoric acid in the presence of magnesium,not only the magnesium but the ferric iron and aluminum impurities ofthe wet process acid as well will tend to form gelatinous colloidalimpurities. By heating the product until it has a moisture content ofless than about 2 percent such gel structure is dehydrated and thefinely comminuted material becomes well suited for stable suspensions.

The term ammonium-containing phosphate as employed herein includesammonium phosphate, magnesium ammonium phosphate and mixtures thereof.The term ammonium phosphate includes mono-ammonium phosphate, diammoniumphosphate and mixtures thereof. The phosphates described herein areunderstood by the art to be ortho phosphates, free from polyphosphates.

The equipment employed to dry ammonium phosphates and dehydrate themetal phosphate gels is not critical to the practice of this invention.For example conventional rotary dryers readily can be employed in orderto drive off the water of crystallization and dehydrate the metalphosphate gel. The final moisture content of the dry product ispreferably less than about 2 percent, and more preferably from about 1to about 1.5 percent, by weight. The final moisture contents are readilyattained in conventional drying equipment. Generally the particlesshould be dried at a temperature of at least about F., with a dryingtemperature within the range of from about to about 200 F. beingpreferred, no polyphosphates being formed at these temperatures.

A wide variety of standard equipment appropriately may be employed tocomminute the dry ammonium phosphates. Such equipment includes, withoutlimitation, ball mills, rod mills, roller mills, pug mills, hammermills, colloid mills or the like. The comminution step is employed todisintegrate the particles to a size appropriate for stable suspensions.The amount of comminution is a matter of choice and frequently becomes abalance between economics and an acceptable minor tendency towardsedimentation. The most desirable particle size is also a function tosome extent of the inherent viscosity of the aqueous medium. In thisregard, high shear agitation tends to be less effective in breaking downthe phosphate particles but may be feasible for suspensions designed foranimal feeds since animal feeds frequently contain molasses whichincreases their viscosity.

It has been determined that milling to provide -35 mesh particles ismost appropriate for the stable aqueous suspensions of this invention.Milling so that all particles pass 35 mesh provides a comminuted productin which often over 90 percent of the particles pass through 200 mesh.Generally a preponderance of the particles pass through a 325 mesh.Generally finer particles produce the more stable slurries and particlesshould be as finely ground as practicable.

Wet comminuting readily provides stable suspensions in a single step andconstitutes one preferred embodiment of this invention. Dry comminutingmay be employed for ammonium phosphates but the equipment tends toglaze. It has been determined that this tendency to glaze may besubstantially reduced if the ammonium phosphates are dry comminuted inthe presence of finely divided nitrogen-free nutrient solids such aspotassium chloride, potassium sulfate, kieserite, M g- SO 'H O,langbeinite, and other salts which are not sensitive to the temperaturesand pressures generated during the dry comminution operation. Drycomminution in the presence of nutrient solids and desirably potashnutrient solids constitutes another preferred embodiment of thisinvention.

The stable agricultural suspensions can, of course, contain other inertagricultural materials in suitably divided form. Thus, the suspensionsmay also contain, for example, calcium phosphate; potash such aspotassium chloride or potassium sulfate; urea; sulfur; and traceminerals such as manganese, boron, copper and the like. In the case ofanimal feed supplements defluorinated phosphates are employed and thesuspension may, in addition, contain carbohydrates, proteins,antibiotics, vitamins and the like.

Suspensions can be formulated to provide a wide variety ofconcentrations. The upper allowable viscosity of any given suspensionis, of course, a function of the particular apparatus in which thesuspension will be handled and applied. Generally, the viscosities willbe below about 2,000 cp. at 78 F. and for some applications theviscosity of the slurry desirably will be below 1,000 cp. at 78 F. Theviscosity of the slurry is a function both of the concentration ofsuspended solids and the inherent viscosity of the liquid. As solublecomponents go into solution the inherent viscosity of the liquidchanges. To the extent any proposed formulation exceeds an acceptableviscosity, the viscosity of the suspension readily may be lowered simplyby adding additional water.

The following examples are included for illustrative purposes only andare not intended to limit the scope of this invention. In the examplesand specification fertilizer analyses are normally given as weightpercents in the order NP O K 0. When magnesium is present as afertilizer nutrient the order of analysis is N-P O -K O-MgO. However,the analyses given in Example VII are weight percents in the order NP-Ksince it is the practice in the feed supplement art to identify theelements rather than the oxides of phosphorus and potassium. Mesh sizesreferred to in this specification are Tyler mesh.

EXAMPLE I A 54% P wet process phosphoric acid containing about 4.3% land A (Fe O +Al O obtained by acidulating Florida phosphate rock withsulphuric acidwas ammoniated to provide monoammonium phosphate(13-52-0). The monoammonium phosphate was dried in a rotary dryer to amoisture content of about 1.5 percent and screened to provide an 8 X 14mesh (-8 +14 mesh) dry granular product. During drying the particlesreached an average particle temperature of about 180 F.

Two thousand grams of the 8 X 14 mesh monoammonium phosphate (13-5 2-0)and 1,060 grams of water were milled in a rod mill for 10 minutes toreduce the particle size of the monoammonium phosphate to 35 mesh. Theresulting slurry had a nutrient content of approximately 8.5-34-0 andwas characterized by a viscosity of 250 cp. at 81 F. after four days ofstatic storage. The slurry remained fluid after 2% weeks of staticstorage and its viscosity measured 560 cp. at 82. F. Slight periodicagitation may be desirable to prevent sedimentation during long periodsof storage.

EXAMPLE II Muriate (potassium chloride having a nutrient content ofabout 60% K 0) was pulverized to provide a 35 mesh material having thefollowing screen analyses:

Mesh /1 Cumulative +65 3.9

Fifteen hundred grams of the 13-52-0 monoammonium phosphate of Example Iwere rotated in a rod mill for 30 minutes to comminute all particles to35 mesh. Thirteen hundred grams of the pulverized muriate then wereadded to the pulverized monoammonium phosphate and the rod mill wasoperated for 10 minutes to ensure complete mixing of the raw materials.Five hundred grams of the mixture, having a calculated nutrient contentof about 7-28-28, were stirred into 200.5 grams of water to provide-astable slurry having a calculatednutrientcontent of about 5-20-20. Theviscosity of the slurry after 3 days was 1,720 cp. at 81 F. The slurryremained fluid after 3 weeks of static storage. a

While the process described in this example produced a stable slurry therods of the ball mill tended to glaze.

EXAMPLE Ill Seven hundred and twenty grams of the 13-52-0 ammoniumphosphate of Example I were dry milled in a rod mill for minutes and1,250 grams of the pulverized muriate of Example II was added. Thematerials were intimately mixed to provide a mixture having a nutrientcontent of about 4.8-19-38. Four hundred grams of the mixture werestirred in 142.8 grams of water to provide a slurry fertilizer having anutrient content of about 3.5-14-28.

The viscosity of the slurry after 3 days of static storage was 1,345 cp.at 81 F. The slurry remained fluid after 3 weeks of static storage.

EXAMPLE iv A slurry having a nutrient content of about 3-12-24 wasprepared by mixing 140.7 parts of the 8.5-34-0 slurry of Ex ample 1,160.1 parts of pulverized muriate of Example 11 and 99.2 parts of water.The final slurry was characterized by a viscosity of 372 cp. at 82 F.While slight periodic agitation was desirable to prevent sedimentation,no gel formation was observed.

EXAMPLE V A slurry having a nutrient content of about 3.25-13-26 wasprepared employing 153.2 parts of the 8.5-34-0 slurry of Example I,173.6 parts of the pulverized muriate of Example 11 and 73.2 parts ofwater. The resulting slurry was characterized by a viscosity'of 1,550cp. at 82 F.

EXAMPLE Vl A 54% P 0 wet process phosphoric acid containing 4.3% I and Aobtained by acidulating Florida phosphate rock with sulphuric acid wasammoniated to provide a diammonium phosphate (18-46-0). The diammoniumphosphate was dried in a rotary kiln to a moisture content of about 1.5percent. During drying the particles reached an average particletemperature of about 180 F.

A slurry fertilizer having a nutrient content of about 7-21-2 l wasprepared from 1,220 parts of 18-46-0 diammonium phosphate, 174 parts ofthe 54 percent wet process phosphoric acid, 1,140 parts of 58% K 0muriate (35 X 200 mesh) and 638 parts of water. The ingredients were wetmilled in a rod mill for 15 minutes at ambient temperature to provide aslurry having a viscosity of 850 cp. at 23 C. The iron and aluminumphosphates present served as viscosity builders so that attapulgite orother viscosity building clays were not necessary to maintain theundissolved solids in suspension.

EXAMPLE VII EXAMPLE VIII A slow release fertilizer was prepared byreacting langbeinite (double sulphate of potash-magnesia), wet processphosphoric acid, and ammonia. The slow release fertilizer containingmagnesium ammonium phosphate was dried to a moisture content below1.5.percent to provide a fertilizer having an analysis as follows:

Nutrient Wt. 7: N 9.8 1 :0 17.7 K,0 1 1.3 MgO A slurry was formedemploying 873 grams of the slow release fertilizer, 533 grams ofdiammonium phosphate, 68 grams of a 30 percent nitrogen aqueoussolution, and 523 grams of water. The ingredients were mixed in a rodmill and the rod milled for 15 minutes. Five hundred and five grams ofthe pulverized muriate of Example II were added to the slurry and therod mill was rotated for a few additional revolutions to homogenize theslurry.

The slurry obtained from the rod mill was about a 8-16-16 -3composition. This slurry was too viscous for normal fertilizerdistribution, and therefore, 167 grams of water were added to decreasethe viscosity. The final slurry was characterized by a nutrient contentof about 7.5-15-l5-2.8 and remained free flowing after 4 days of staticstorage. The viscosity of the slurry was 775 cp. at 81 F.

The free flowing slurry of Example VIII is in direct contrast to theslurry formed when soluble magnesium is added in conjunction with anammonium phosphate. Water, aqueous ammonia, comminuted (-35 mesh)diammonium phosphate produced according to this invention, pulverizedlangbeinite and pulverized 60% K muriate were mixed to provide a slurrythat had a nutrient content of about 7.5-l-l5-2.8. While this latterformulation initially resulted in a fluid slurry, the slurry hadcompletely gelled to form a solid mass after standing overnight.

Since modifications of the invention will be apparent to those skilledin the art it is intended that the invention be limited only by thescope of the appended claims.

Iclaim:

1. A process for forming aqueous fertilizer and animal feed supplementsuspensions which comprises ammoniating phosphoric acid containinggel-forming impurities which are compounds of metals from the groupconsisting of iron, aluminum, magnesium and mixtures thereof, saidimpurities being present in amounts producing a weight ratio of saidmetals expressed as oxides, to the P 0 content of the acid, which isgreater than about 0.05, thereby obtaining an ammonium-containingphosphate having gelatinous, colloidal impurities therein, heating saidammonium-containing phosphate at a temperature within the range of about130 to about 200 F. to dehydrate the gel structure of said gelatinous,colloidal impurities and obtain a dried ortho-phosphate product, freefrom polyphosphates, having a moisture content of less than about 2percent by weight, comminuting said dehydrated ammonium-containingphosphate to finely-divided particles substantially all of which passthrough a 35 mesh screen, Tyler standard, and dispersing said dehydratedparticles in water whereby an aqueous suspension is formed.

2. The process of claim wherein said phosphoric acid is a wet processphosphoric acid containing normally incident iron and aluminumimpurities.

3. The process of claim 2 wherein said ammonium-containing phosphate isdried at a temperature of from about 150 to about 200 F.

4. The process of claim 3 wherein said dehydrated ammonium-containingphosphate is comminuted in the presence of water to provide a stableaqueous suspension.

5. The process of claim 4 wherein said wet process phosphoric acid isammoniated in the presence of an added water-soluble magnesium compoundto provide a composition containing magnesium ammonium phosphate.

6. The process of claim 5 wherein the magnesium compound is a magnesiummineral containing a magnesium salt and a potassium salt.

7. An aqueous suspension consisting essentially of a suspension in waterof a finely divided ammonium-containing phosphate produced from wetprocess phosphoric acid by ammoniating wet process phosphoric acidcontaining gel-forming impurities which are compounds of metals from thegroup consisting of iron, aluminum, magnesium and mixtures thereof, saidimpurities being present in amounts producing a weight ratio of saidmetals expressed as oxides, to the P 0 content of the acid, which isgreater than about 0.05, thereby obtaining an ammonium-containingphosphate having gelatinous colloidal impurities therein, heating saidammonium-containing phosphate at a temperature within the range of aboutto about 200 F. to dehydrate the gel structure of said gelatinous,colloidal impurities and obtain a dried orthophosphate product, freefrom polyphosphates, having a moisture content of less than about 2percent by weight, comminuting said dehydrated ammonium-containingphosphate to finely divided particles substantially all of which passthrough a 35 mesh screen, Tyler Standard, and dispersing said dehydratedparticles in water whereby an aqueous suspension is formed.

8. The aqueous suspension of claim 7 containing a mixture of iron andaluminum ammonium phosphates.

9 I UNFFED STATES PATENT -C?' HCE CE T QAT o1 rcoemaGyms:

Patent No. 3 4656 931' v Baked Y April 18 1972 Tiw n h) William B. DancyIt is Certified that error appears in the above-identifiedv patent; andthat said Letters Patent are hereby corrected as shown below:

I r Column 6 line 37, "7 21 2" should read 7-21 -21-; line 38, "1"should be eliminated.

Co1umn6, line 50, "(18-204 should read (18-20-0)--;

line 51, should be eliminated.

Column 8, line 3, a te ficlaim", -'-1-- should be added.

Signed and sealed this 2nd day of Januaryl973.

(SEAL) Attest:

EDWARD M.,FLETCHER,JRQ ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. The process of claim wherein said phosphoric acid is a wet processphosphoric acid containing normally incident iron and aluminumimpurities.
 3. The process of claim 2 wherein said ammonium-containingphosphate is dried at a temperature of from about 150* to about 200* F.4. The process of claim 3 wherein said dehydrated ammonium-containingphosphate is comminuted in the presence of water to provide a stableaqueous suspension.
 5. The process of claim 4 wherein said wet processphosphoric acid is ammoniated in the presence of an added water-solublemagnesium compound to provide a composition containing magnesiumammonium phosphate.
 6. The process of claim 5 wherein the magnesiumcompound is a magnesium mineral containing a magnesium salt and apotassium salt.
 7. An aqueous suspension consisting essentially of asuspension in water of a finely divided ammonium-containing phosphateproduced from wet process phosphoric acid by ammoniating wet processphosphoric acid containing gel-forming impurities which are compounds ofmetals from the group consisting of iron, aluminum, magnesium andmixtures thereof, said impurities being present in amounts producing aweight ratio of said metals expressed as oxides, to the P2O5 content ofthe acid, which is greater than about 0.05, thereby obtaining anammonium-containing phosphate having gelatinous colloidal impuritiestherein, heating said ammonium-containing phosphate at a temperaturewithin the range of about 130* to about 200* F. to dehydrate the gelstructure of said gelatinous, colloidal impurities and obtain a driedortho-phosphate product, free from polyphosphates, having a moisturecontent of less than about 2 percent by weight, comminuting saiddehydrated ammonium-containing phosphate to finely divided particlessubstantially all of which pass through a 35 mesh screen, TylerStandard, and dispersing said dehydrated particles in water whereby anaqueous suspension is formed.
 8. The aqueous suspension of claim 7containing a mixture of iron and aluminum ammonium phosphates.